Dynamic changes of the anti- and pro-apoptotic proteins Bcl-w, Bcl-2, and Bax with Smac/Diablo mitochondrial release after photothrombotic ring stroke in rats

The anti-apoptotic proteins Bcl-w and Bcl-2 and the pro-apoptotic protein Bax may mediate cell death or survival via regulation of the mitochondria including second mitochondria-derived activator of caspase (Smac)/direct inhibitor of apoplosis protein (IAP)-binding protein with low pl (DIABLO) release. This study aimed to explore alterations in Bcl-w, Bcl-2, and Bax and the relationship between these proteins and Smac/DIABLO by means of in situ hybridization, immunohistochemical (IHC) staining, and Western blots after low- and high-intensity photothrombotic ring stroke. At 4 h after low-intensity irradiation, we found widespread bcl-w overexpression on both the mRNA and protein levels in the bilateral cortex except the ring lesion region and in subcortical regions. A prolonged elevation of Bcl-2 with relatively unchanged Bax in the mitochondrial fraction was demonstrated from 4 to 72 h. These upregulated anti-apoptotic proteins combined with little Smac/DIABLO release might be associated with increased cell survival and thereby remarkable morphological recovery after low-intensity irradiation. After high-intensity irradiation, we observed decreased bcl-w and bcl-2 mRNA with increased Bcl-2 protein in the cytosolic fraction, whereas the Bax protein remained in scattered ischaemic cells in the ring lesion and the region at risk that corresponded with release of Smac/DIABLO from mitochondria to the cytosol at 1-24 h. These changes might be related to the massive cell death observed after high-intensity irradiation. Taken together, the balance and the location of anti-apoptotic proteins vs. pro-apoptotic proteins could be associated with the translocation of Smac/DIABLO from the mitochondria to the cytosol and therefore closely related to cell death or survival after focal cerebral ischaemia.